What a cadence is
It is the harmonic formula that closes a phrase, like punctuation in a text. The main ones, in C major and A minor:
Types
- Perfect (perfect authentic): V(7) – I with both chords in root position and the tonic in the soprano. G7 – C; in minor E7 – Am. It is the full stop.
- Imperfect (imperfect authentic): V – I but with inversions or with the third/fifth in the soprano. G7/B – C. It is a strong comma.
- Half cadence: the phrase stops on the V. C – F – G or Dm – G. In minor the Phrygian half cadence iv6 – V: Dm/F – E.
- Plagal: IV – I, F – C (the “Amen” cadence). A very pop and gospel variant: minor plagal iv – I, Fm – C.
- Deceptive (evaded, interrupted): V – vi, G7 – Am; or V – bVI, G7 – Ab. The ear expects the tonic and receives a substitute: it serves to lengthen the phrase.
Useful rules
- In the perfect cadence the leading tone (B) rises to C and the seventh (F) falls to E.
- In the deceptive cadence in major, double the third of the vi chord (C in Am) to avoid parallel fifths.
- In pop songs cadences are often implied: a loop without a V has no true cadences, and the closure is achieved through arrangement and melody.
Real example
The chorus of “Let It Be” (Beatles, C major) closes with F – C: a plagal cadence. “Walking on Broken Glass” (Annie Lennox, 1992) is often cited as an example of the deceptive cadence in pop.